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장현구,윤용구 대한금속재료학회(대한금속학회) 1971 대한금속·재료학회지 Vol.9 No.3
燒結 알루미늄 固體蓄電器의 製造 條件과 電氣的 特性에 對하여 硏究하였다. 燒結陽極素子의 有孔度는 粘結劑의 含量과 成型壓力을 變化시켜 주므로 調節하였다. 3% 붕산암모늄 수용액 중에서 陽極酸化시켜 多孔質素子의 表面上에 誘電皮膜을 입혀 주었다. 질산망간의 熱分解에 의하여 誘電酸化皮膜上에 固體電解質을 被覆 하였으며 熱分解와 再化成을 數回 반복하였다. 이와같이 製造된 燒結 알루미늄 固體蓄電器의 電氣的 特性은 알루미늄 電解蓄電器 보다는 優秀 하였지만 탄탈 固體蓄電器 보다는 劣等 하였다. g당 容量 2,450 μF·V를 얻었지만 漏洩電流는 아직도 充分히 낮추지 못하였다. 이 事實은 알루미늄의 燒結溫度가 낮기 때문에 陽極素子內에 不純物이 철저히 除去되지 못함에 기인한다고 생각된다. Fabrication variables of sintered aluminum solid capacitors were studied in relation to their electrical properties. The porosity of anode pellets was controlled by varying the content of binder and compacting pressure. The dielectric oxide layer on the porous surface of sintered anode pellets was formed by anodizing in 3% ammonium borate aqueous solution. The solid electrolyte on the dielectric oxide layer was applied by pyrolysis of manganese nitrate. Pyrolysis and reformation at a reduced voltage were repeated a few times. Electrical properties of sintered aluminum solid capacitors so fabricated were superior to those of aluminum electrolytic capacitors whereas they were inferior to those of sintered tantalum solid capacitors. A capacitance-voltage product of 2.450 μF·V/gram was achieved but a sufficiently low leakage current was not achieved as yet. This fact may be attributable to low sintering temperature and consequently, relatively high contents of impurity remaining in sintered anode pellets.
超音波 C-Scan을 利用한 構造用 세라믹스의 機械的 特性評價
장영권,백영남 慶熙大學校 材料科學技術硏究所 1989 材料科學技術硏究論集 Vol.2 No.-
Computer - aided high frequency ultrasonic is applied to aluminum oxide (85w%, 94w%, 96w% and 99w%) MOR (modulus of rupture) samples to evaluate mechanical properties such as density variation, pore content, plastic modulus, shear moudlus and poisson's ratio. Ultrasonic wave velocity and attenuation measurement techniques were used as an evaluator of such properties. Pulse-echo C-Scan images with different gate setting method using 50㎒ center frequency one inch focal length transducer allows evaluation of density variation and pore content. Elastic modulus calculated with the relation of density and ultrasonic velocity. It shows better reliability as compares with resonance method. Sintered density variation of 0.025g/㎤, that is 0.6% of theoretical density in Al_(2)O_(3) samples can be observed by ultrasonic velocity measurement. Attenuation measurement method qualitatively agree with 4-point fracture testing result concerning of porosity content.
Direct band gap carbon superlattices with efficient optical transition
Oh, Young Jun,Kim, Sunghyun,Lee, In-Ho,Lee, Jooyoung,Chang, K. J. American Physical Society 2016 Physical review. B Vol.93 No.8
<P>We report pure carbon-based superlattices that exhibit direct band gaps and excellent optical absorption and emission properties at the threshold energy. The structures are nearly identical to that of cubic diamond except that defective layers characterized by five- and seven-membered rings are intercalated in the diamond lattice. The direct band gaps lie in the range of 5.6-5.9 eV, corresponding to wavelengths of 210-221 nm. The dipole matrix elements of direct optical transition are comparable to that of GaN, suggesting that the superlattices are promising materials as an efficient deep ultraviolet light emitter. Molecular dynamics simulations show that the superlattices are thermally stable even at a high temperature of 2000 K. We provide a possible route to the synthesis of superlattices through wafer bonding of diamond (100) surfaces.</P>
國産 Rhodochrosite로부터 黃酸망간 浸出時 不純物 除去에 관한 硏究 (제2보)
金城權,崔昌鎭,金英玉 圓光大學校大學院 1987 論文集 Vol.1 No.-
The purpose of this investigation is to study efficiency of the impurities removal and leaching efficiency of manganese(Ⅱ) sulfate on the pH when we make pure manganese (Ⅱ) sulfate by the leaching from the medium-grade domestic rhodochrosite ore under the best conditions. Leaching process is carried out by treating the sample with sulfuric acid to extract out the manganese (Ⅱ) sulfate, thereafterto experimentally obtain the content of each component in leached solution. The Leaching efficiency-pH relations of manganese(Ⅱ)sulfate was measued in MnSo₄ solutions as function of pH with Ca(oH)₂-BaS. Then removal efficiency-pH relations of Iron was measured in MnSo₄ solutions as function of pH with Ca(oH)₂. The best pH-response of the efficiency of Iron removal was obtained as above 94.2% in Ca(oH)₂solutions in the pH range 5.0. The leaching efficiency and the removal efficiency-pH relations of impurities (magnesium) was measured in MnSo₄ solutions as function of pH with NH₄(OH) and NH₄(OH)-BaS. With the intention of obtain the best conditions of impurities pH relations, leached substances were investigated by means of I.C.A.P analysis, Atomic absorption spectra, X-ray diffraction, Infrared spectra and chemical analysis.
Large infantile hemangioma with subfascial location: a case with difficulty of clinical diagnosis
( Dae-lyong Ha ),( Woo-il Kim ),( Min-young Yang ),( Won-ku Lee ),( Tae-wook Kim ),( Sung-min Park ),( Hyun-joo Lee ),( Gun-wook Kim ),( Hyun-chang Ko ),( Byung-soo Kim ),( Moon-bum Kim ),( Hoon-soo K 대한피부과학회 2018 대한피부과학회 학술발표대회집 Vol.70 No.1
The unexpected finding of newly growing lump in an infant induces anxiety to parents and results in an urgent visit to hospital. Before performing invasive interventions for this infant patient, benign conditions like infantile hemangioma (IH) should be excluded as it could show variable clinical characteristics. A 6-month-old girl was presented with protruding skin-colored tumor on right upper back, with approximately 10cm in diameter and without surface change. The tumor abruptly enlarged over the period of 2 weeks without any previous episode. MRI showed a lobulated hypervascular mass in the subfascial layer with neovascularization inside. Through this findings, thought by radiologist and orthopedic surgeon to be malignant tumor, exploratory surgery was planned. Before surgical excision, this patient was consulted to our department. As the lesion was softly palpable and movable, incisional biopsy was performed to rule out the benign tumor like deep type IH. Histopathologic examination showed numerous vessels lined by plump endothelial cells. Immunohistochemical staining revealed the positivity of endothelial cells for CD-31, GLUT-1. Under the diagnosis of IH, the patient received oral propranolol medication for 1 year. Following the patient, we found the tumor diminished dramatically in volume. Although IHs are common benign tumor in infancy, Subfascial location is unfamiliar and rare. So, we herein report a case of subfascial lH.
몰리브덴인산화물 촉매에 의한 메틸피라진의 가암모니아 산화반응
신채호,장태선,조득희,이동구,이영길 ( Chae Ho Shin,Tae Sun Chang,Deug Hee Cho,Dong Koo Lee,Young K . Lee ) 한국공업화학회 1997 공업화학 Vol.8 No.5
몰리브덴산암모늄염과 인산의 반응으로 P/Mo=0.6의 비율을 가진 몰리브덴인산화물을 제조하고 이를 촉매로 사용하여 메틸피라진의 가암모니아 산화반응에 대한 메틸피라진, 산소, 암모니아의 각각의 분압과 반응온도 등의 반응변수의 영향을 살펴보았다. 표준실험조건하의 반응에서 300시간까지의 촉매활성은 안정상태를 유지하였다. 안정화 상태에서의 메틸피라진의 가암모니아 산화반응 속도식은 -r=kP_MPP_NH3 °P_02^γ(γ=2.2;1.3≤P_02(kPa)≤4)으로 메틸피라진에 대해서는 1차, 암모니아에 대해서는 0차, 산소에 대해서는 분압 4kPa이하에서 2.2차로 나타났다. 623 K이하의 반응온도 하에서의 겉보기 활성화에너지는 29.6㎉/㏖이었다. 메틸피라진의 주생성물은 시아노피라진으로서 선택도는 전환율에 관계없이 항상 90%이상을 유지하였다. Molybdenum phosphate(P/Mo = 0.6) has been synthesized with ammonium molybdate and phosphoric acid under aqueous solution. The kinetics of the ammoxidation of methylpyrazine over molybdenum phosphate catalyst was investigated with the variation of reaction temperature and partial pressure of methylpyrazine, oxygen and ammonia, respectively at atmospheric pressure. The catalytic activity was constant for 300hrs operation under our experimental conditions. Under the steady-state condition, the rate equation of methylpyrazine was shown as -r=kP_MPP_NH3 °P_02^γ(γ=2.2;1.3≤P_02(kPa)≤4). The apparent activation energy was 29.6㎉/㏖ below 623K. The main product obtained in the ammoxidation of methylpyrazine is cyanopyrazine whose selectivity was kept always over 90% regardless of conversion.
Ui-Gum Kang,Hyang-Mi Park,Jee-Yeon Ko,Jae-Saeng Lee,Weon-Tai Jeon,Chang-Young Park,Ki-Do Park,Vladimir K. Chebotar 한국토양비료학회 2017 한국토양비료학회지 Vol.50 No.3
In order to obtain promising rice growth-promoting microbial strains that can be used as substitutes for chemical fertilizers, 172 bacterial strains were isolated from rice roots grown in Korean and Russian soils. Out of them, the strains KR076, KR083, KR181 and RRj228 showed plant growth-promoting activities on maize seedlings. Bacillus megaterium KR076 and Bacillus sp. KR083 showed both nitrogen-fixing and plant growth-promoting activities, while Rhizobium sp. KR181 and Pseudomonas sp. RRj228 appeared to support only plant growth-promotion, but not N2 fixation. Especially, RRj228 showed high growth promoting activity at low concentrations. Inoculation studies with KR083 and RRj228 revealed a high affinity to the Japonica rice variety such as Junambyeo than the Korean Tongil type variety such as Arumbyeo. Both KR083 and RRj228 strains showed rhizoplane and/or endophytic colonization in Japonica and Tongil types rice when soaked with the bacterial suspension of 1.1 × 10<SUP>5</SUP> cfu ml<SUP>-1</SUP> for six and twelve hours. However, the total bacterial cell numbers were higher in the roots of Japonica variety than in the Tongil type. In inoculation trials with Daesanbyeo rice variety, the seedlings inoculated with KR181 and RRj228 at the rate of 2.0 × 10<SUP>6</SUP> cfu ml-1 showed yield increment of 35% and 33% (p < 0.01), respectively, so that they contributed to the replacement of chemical fertilizer at half doses of N, P₂O<SUP>5</SUP>, and K2O in pots. In Junambyeo rice seedlings, the strain RRj228, when inoculated with a cell suspension of 1.8 × 10<SUP>6</SUP> cfu ml<SUP>-1</SUP>, promoted 3.4% higher yield at 70% dose than at a full dose level of N 110 kg ha<SUP>-1</SUP> in field. These results suggest that the rhizobacteria KR181 and RRj228 are prospective strains for enhancing rice performance.
High-Pressure Synthesis of $SmFeAsO_{1-x}F_x$(x=0.2) Single Crystals
이현숙,박재현,이재엽,김주영,조병기,정창욱,이후종,Lee, Hyun-Sook,Park, Jae-Hyun,Lee, Jae-Yeap,Kim, Ju-Young,Cho, B.K.,Jung, Chang-Uk,Lee, Hu-Jong The Korean Superconductivity Society 2009 Progress in superconductivity Vol.10 No.2
Fluorine-doped $SmFeAsO_{1-x}F_x$ single crystals with the nominal value of x=0.2 were grown at $1350-1450^{\circ}C$ under the pressure of 3.3 GPa by using the self-flux method. Plate-shaped single crystals in the range of a few-150 ${\mu}m$ in their lateral size were obtained. The detailed crystal structure was analyzed by using the x-ray diffractometry. Superconducting transition temperature, determined by the resistive transition, of a single crystal was about 49 K with a narrow resistive transition width of ${\sim}1$ K. A relatively sharp transition, a low residual resistivity, and a large residual resistivity ratio compared with those reported for $REFeAsO_{1-x}F_x$(RE=Sm, Nd) single crystals indicate the high quality of our single crystals.